Variable-speed transmission



Sept'. 6 1927. 5 1,641,692

R. H. lRATT VARIABLE SPEED TRANSMISSION File'd Oct. 2, .1926 6 Sheets-Sheet 1 Sept.' l6, 1927. R. H. PRATT VARIABLE SPEED TRANSMISSION .Y

Filed Oct. 2. 1926 6 A Sheets- Sheet v2 akamu Sept. 6, 1927. 1,641,692

R. H. PRATT VARIABLE SPEED TRANSMISSION Filed 001.2, 192e l @Sheets-,sheet 3 anonimi Mss Hfpazm l l 641 692 Sept. 6,1927. R. H. PRATT VARIABLE SPEED TRANsMIssIoN Filed ocyz. 1926 eheetsfsheet 4 n. Il

- R055 HRATT Se'pt. 6, 1927.

A 1,641,692 R. H. PRATT VARIABLE SPEED TRANSMISSION A Filed esta. 192e e sheets-sheet 6 Patented Sept. 6, 1927.

narran erases tentez ROSS H. PRATT, OFVASHINGTOT, DISTRICTOF COLUMBIA.

. VARIABLE-swan TnnNsMissioiv;

Application `i'iled 4October 2, 1925. Serial No. 139,170.

This invention relates to variable speed transmissions, and more particularly to variable speed transmissions especially designed for use in connection with motor vehicles.

It is a major purpose of the present invention to provide a `variable speed transmission of the so-called worm type7 wherein varia-V tion of speed is had through operatively engaging worms of varying pitches with a clutch-controlled driving gear operatively connected with the driven member or'rear axle of tliemotor vehicle.

It is a further object of the. present invention to lprovide an improved transmission wherein acceleration or deceleration of speer may be conveniently had, and wherein, if desired, the change may be readily made from a high to a lower` gear for the purpose of utilizing the engine as a braking power when descending grades, It is a still further purpose of the present invention to provide an improved transmission wherein a change to a. slow speed is made easy when traffic conditions require the same, without cutting oil' the Vfuel supply or otherwise reducing the pulling power of the engine or overburdening the engine by excessive application of brakes, the lower speed or gear giving the engine greater leverage and eliminating the danger of stalling on railway or street car tracks or in other dangerous places when drivingslowly. Y Y

In the general type of .so-called sliding gear transmissions, wherein a gear must be broughtfrom a position at rest into engagement with anotherV gear kthrough a sliding movement, it is difcult and often impossible to eect such engagement when the speed at which the vehicle is travelling is greater than the speed at which the enginel shaft is revolving, which is generally the condition when the vehicle is descending a grade. Ae cordingly withthe aforesaid sliding gear type of transmission it becomes dangerous and in most instances impossible to accom-- plish such a shifting of gears to utilize the braking power of the engine at a lower speed. use of a plurality of 'differently pitched worms adapted to selectively engage or mesh with a driving gea-r, Aany desired changeor variation from a high to a lowergearor vice versa may be lconveniently had.

lt is afurther object of the present invention to provide an improved'transmission relatively silent or noiseless, of the type set In the present invention, with the forth, which will drive as silently in its low or intermediate speeds as in its high speed or gear; all speeds being a direct drive from the engine shaft. It is a still further object of the present invention to provide in a variable speed transmission of the type set forth means for 'automatically operating the novel clutch connectionl between the ldrive and driven members.

Transmissions of the worm type are.at

present manufactured wherein ar worm secured upon the drive shaft engages with a worm gear mounted'upon the driven member or rear axle. These transmissions in order to permit of the vehicle coasting7 as .under its own momentum, must of necessity have ltne pitch of .the worm on the drive shaft extremely steep. Thisresults in a rela# tively great degree of side thrust causing waste of power in starting and' frequent stripping and damaging of worms, gearsl and other parts. Y It is accordingly 'a major ob-y jeet'o'i" the present invention to provide means'whereby a relatively lower pitched worm might be as conveniently employed, particularly for starting and for running in low and reverse speeds, such means comprising the mounting of the driving gear, co'm-l f monly called the ring gear upon the driven member with Va clutch VconnectionA therebetween.

It is a f urther object of the present invention to provide novel driving gear which will readily and conveniently properly en gage or mesh with any one of a desired plurality yof differently pitched worms.

It is a still further object of the present invention to provide novel clutch control mechanism for the driving gearg novel means for shifting any desired one of the` various worms into engagement with ,the

and Ynovel featuresthereof will be hereinf after more fully set forth.

' The accompanying drawings illustrate one practical transmission embodying the invention which will be describedI in detail to enable others to understand and use the same,

loo

but the invention is not considered restricted to the specific construction shown in the drawings, and reference is therefore had to the claims for summaries of the essentials of the invention and of the novel features of construction and of the novel combinations of parts for all of which protection is desired.

Y As shown in the drawings:

Figure 1 is a longitudinal sectional lview through theentire transmission, parts being broken away, illustrating the operative mechanism therefor. f

Figure .2 is atransverse sectional view taken on the line 2 2 of Figure 1, illustrating the driving gear, the clutch therefor and associated parts in operative or engaged position.

, yFigure 3 is a sectional View similar to Figure 2, illustrating the driving gear, the

Clutch therefor' and theassociated mecha- Y nism in inoperative or disengaged position.

Figure 4 is a detail sectional-view taken ,on the line H of Figure 2, locking in the direction of the arrows.

Figure 5 is a detail sectional view taken on the line 5--5 of Figure 2, looking in the direction of the arrows.

Figure 6 is a. detail,v sectional View taken en the line 6-6 of Figure 2, looking in the direction of the arrows. Y

' Figure 7 is a detail sectional view taken on the line 7-7 of Figure 2, looking in the direction of the arrows.

Figure 8 is a detail sectional View taken on the line 88 of F igure'l, looking in the direction of the arrows, illust-rating the extension sleeve and locking mechanism therefor., controlling the shifting of the various worms into engagement with the driving gear.v f v VFigure 9 is a detail sectional view taken on the line 9-9 of Figure 8, looking. in the direction of the arrows, illustrating the Vlock 'i 15 member' and controlling' levers for securely retaining the extension sleeve in any desired position. Figure 10 is a detail sectional view similar to Figure 9, illustrating ther lock member 00 and levers in disengaged position.

Figure Vl1 is a detail sectional view taken bn the line 11-11 of Figure 8.

Figure 12 is a detail sectional view taken on the. line 12-12 of Figure 1', illustrating for.

Figure 1S isa detail sectional view taken on the linelB-l of Figure 12, illustrating Y the' shifting lever guide bracket.

Figure 14 is a diagrammatical view illustrating the developmentof the cross sectional shape on onel of the teeth on the driving gear capable of proper engagement with any desired one `on the different-ly $35 pitched Worms,v Y

the Yshifting lever and guide bracket there- Figure 15 is a diagrammatical View illustrat-ing the proper angular relationship, in

plan view, developed, of the teeth on the driving gear.

As shown in' the drawings, a drive shaft 1, carrying a plurality of worms 2, 3, l and 5 of varying pitches rigidly secured thereto, is slidably mounted within suitable bearings 1a of any desired type, properly positioned within the transmission housing or casing C. The shaft 1 is mounted for endwise movement and may be provided with sleeve-.like bushings adapted to engage wit-hin the bearingsL 1a.

Suitably positioned adjacent the rear of the transmission housing,and preferably beneath the drive shaft, is the ydriven member, comprising'the rear end of the motor vehicle. As .is usual in motor vehicle construction, this rear end comprises a pair of axially aligned axles or shafts 6 having their inner extremities terminating in the usual differental (not shown) mounted wthin the usual differential housing 7. The differential housing 7 is provided on one side thereof with asleeve extension 7a, and upon this extension is mounted the driving gear 8 and the associated parts therefor as will be hereinafter more fully described. The driving gear 8 is adapted to selectively engage or mesh with any desired one of the various worms mounted upon the drive, andv is provided with teeth Separticularly conformed so as to properlyengage or-mesh with such worms. Y

A suitable housing or casing isV provided for the rear end, such housing preferably forming an integral part of the transmission housing. Suitable bearings 7b, of any desired type, are provided, one preferably adjacent the extremity of the sleeve yextension 7a and the other adjacent the opposedV side of the differential housing for the proper aligning of the differential andthe shaftsY or aXles 6. y

The gear 8 is mounted for free rotation upon a sleeve 8a splined as at 8" or otherwise slidably mounted upon theextension 7a. This sleeve 8a is provided adjacent the inner extremity thereof with an upturned fiange 8C adaptedV to bear against the face of the differential housing when lthe driving gea-r is in engaged position as shown in Figure 2. Obviously, engagement of the driving gear 8 with any desired one of the worms mounted upon the drive shaft will resultin the rotation of the gear 8 in the desired direction and Aat the desired rate ,of speed.

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Suitable.mechanism is provided to recip-f recate the ydrive Vshaft to selectively bring any desired worm into enga-gement with the driving gear and at the same time to disengage the driving gear and withdraw thel same from the path ofthe drive shaft during the period of transition.

The driving gear 8 has associated therewith a suitable clutch, of any desired type, properly mounted upon the sleeve 8a. There has been illustrated in the drawings the usual type of disc clutch 8b, comprising the usual outer drum preferably forming an integral part of thedriving gear 8, inner drum keyed or otherwise secured to the sleeve 8a, discs, clutch push ring, driving plate, and clutch lingers, all as are well known in the art. Obviously any other type of clutchv might be used. he clutch is adapted to be held in engaged position by the pressure of a coil spring Se interposed between the recessed leek-nut 8f secured upon the sleeve 8?u adjacent the extremity thereof, and a clutch shift ring 8g freely mounted upon the sleeve. The clutch shift ring is provided with a centrally located turned down portion adapted for engagement by the inturned extremities 9C of a Vclutch fork 9b secured to a countershaft 9 mounted within suitableA bearings 9a on the inner face of the transmission housing.

Rotation of the shaft 9 in a clockwise direction will first result in the compression of the coil spring Se, the ring 8g being retracted until it abuts against the inner face of the lock nut 8f. At this point the clutchA will have become disengaged and the driving gear will be free to rotate upon its sleeve, the load of the vehicle -or pressure having ieen removed therefrom. Completion of the rotation ofthe shaft 9 will then result in the movement of the entire sleeve 8, carrying the .driving gear therewith so as to withdraiv the same from the path of the drive shaft l and worms thereon; the parts assuming the position as illustratedin Fig ure 3 of the drawings.. f

lt will'be readily understood that with the driving gear 8 in engagement with any one of the worms on the drive shaft, upon the release of the clutch the load will have been removed therefrom, and there being no relative pressure between such worm and the driving gear, it will accordingly beV an easy matter to bodily slide or withdraw the gear from engaged posit-ion. The bearing 7b adjacent the sleeve 7a has an extension ythereon internally screw-threadedl forV engagement with the extremity of the said sleeve, a coil spring 8h being interposed around the sleeve between such extremity and the opposed face of the sleeve 8a. Rotation of the shaft 9 to cause the clutch fork to fully act to withdraw the driving gearinto disengaged position will result in the compression of the coil' spring Shwhile upon the release of the clutch fork the said spring will act to return the sleeve 8 and the driving'gear 8 therewith into engaging position. j

Suitable mechanism is provided to properlyl move the drive shaft 1 endwise within its bearingsia to bringthe desired worm,

into position for engagement with the driving gear. As shown in FigureY 8of the drawings the drive shaft has one extremity thereof rigidly secured in any desired manner to one end of a telescopic tubular member 10, as by beingscrew-threaded into a block 10a securely retained within the member'lO as by pins or the like l0. The opposed end ofthe member lO is provided with 'a guide aperture as at l()c through which is adapted to freely pass the engine or power shaft S which preferably has the usual universal joint J properly locatedv thereon, as is lwell known in the art.

`Preferably the bore of the telescopic member l0 is substantially square in cross section; the inner extremity of the shaft S being provided with a block 10d adapted to snugly `lit within the said bore thus assuring the proper rotation lof the drive shaft through the member 10. The Vtelescopic member 10 is adapted toslidje upon th-e block l0d and carry therewith the drive shaft l to I properly selectively shift the desiredfworm into position for engagement with the driving gear. A shifting collar 10e is mounted upon the drive shaft between lock washers lOf, the collar vhaving van upwardly directed extension forming a ball and sockety joint 1la for connection with a shifting rod 1l passing forwardly through the transmission housing and having at its extremity a pin and slot connection 12a with a link l2 for a purpose to be hereinafter more fully described.v It will be clearly understood that movement of the shifting rod 1l will result in endwise' movement ofthe entire drive shaft within the bearings la, and at the same time identical movement willbe imparted to the telescopic member l0 secured to the inner end of the drive shaft. There has thus been described anv extensible driving connection between'the drive and engine shafts, obviouslyany other type of connection might be as vconveniently used, thatjshown being preferred. y l v Y lt will be noted that the worm 2 is relatively low in pitch, the' worms 3 and fl being increasingly more steeply pitched, re.- spectively, in the same direction as the pitch of the Worm 2; the worms 2, 3 andll being intended to control respectively the low, intermediate and high speeds of the transmission. The worm 5 is oppositely pitched with respect to the other worms, and accordingly is intended to control the reverse speed. A spacing ring 5a is secured to the drive shaft l between the low speed worm 2 andl the reverse speed wormv 5 to provide a space for a neutral Vposition forthe drive shaft and the driving gear without'thenecessity of the driving gear being withdrawn from position in alignment with the drive shaft. .4 Movement of the vshiftingl collar l()e in one direction starting from. the neutralv jill position will successively bring the forward driving worms'27 3 and 4 vinto position for engagement with the driving gear; move- Yment of the said shifting collar in the opin the transmissionhousing, .see Figures 8 to 10 inclusive, thus preventing endwise movement of the drive shaft when such arms are in engaged position. The number of such notches corresponds to the number of proper positions ofthe driveshaft,l in the present disclosure--revers-e, neutral, low, intermedia-te and high. The number of'such positions would of course depend on the desired number ofspeeds and could be varied at will. The lock member 10h is provided with an integral downwardly directedarm 10k pivotally connected by a link 101 which in turn has a Afree pivotal connection lwith a rod 10 mounted in a pair of arms or levers 100 keyed or otherwise secured to the countershaft 9. 1 Y l Y Partial rotation of the shaft 9 to release the clutch 8d and withdraw the driving gear from the path of the drive shaft as above described, will at the saine time, through theY levers 101, 1()m and 10, result in the movement of the Vlock member to the position shown in Figure 10 of the drawings, thus disengaging the arms of the lock member t from the notches 10j and permitting the endwise shifting of the drive shaft. Upon the drive shaft having been properly shifted to the desired position, the return of thek shaft .9 Vto its normal position will permit the arms l()i of the lock member to engage with one of the notches 1()j preventing any further endwise movement or end Ythrust imparted tothe drive shaft.V l

Anydesired ymeans may be provided for 5*' the proper shifting of the drive shaft to gear.

bring any desired' one of the worms into position for engagement with the driving In the preferred embodiment of the 1present invention, and as illustrated more 'l particularly in Figure 12 of the drawings,

such means comprises a shifting lever 14, pivotally secured as at 14 to an arm 13 keved 'or' otherwise rigidly secured to the shaft 9.

y Mounted upon any suitable place as the 'lt dash or instrument board B of the vehicle isa bracket or guide lprovided with'a slot 15a in which the levery 14 is guided. This slot is provided along one side thereof with a plurality of cut-away portions or notches Y A properly marked, as indicatedin' Figure 13 Vith the lever' 14 seated within any one of the notches in the guide bracket 15, the shaft 9 will be in its normal position and the clutch 8d will be disengaged, the driving gear being in perpendicular-ly aligned position with relation to the drive shaft.

Movement of the lever 14 from the notch to the slot 15a will result, through the arm 13,

in the impartation of a sufficient rotaryV movement to the shaft 9 to result in the Vwithdrawal of the driving gear from the path of the drive shaft, the various parts assuming the position as illustrated in Figure 3. rlhe vshifting lever may then be moved within theslot 15a, through the pivotal connection ofthe lever with the arm 13, to seat the lever in any desired notch and cause the shifting of the drive shaft to selectively engage the desired worm with the driving gear.

A link 12" is pivotally connected to the lever 14 adjacent the upper extremity kthereof, the said link having at its opposite end a ball and socket connection with the lever Y12 pivotally mounted as at 12d. The lower end of the lever 12 has, as previously .def scribed, a pin and slot connection 12 with the shifting rod 11. the lever 12 is located 'adjacent the upper extremity thereof thus' providing a greater movement to the lower end of the lever 12 where connection is had with the shifting rod 11 controlling the direct movement vof the drive shaft. Accordingly a relatively small degree of pivotal movement of the shift-ing lever will result in a considerablyY greater degree of movement being imparted to'the shifting rod 11; ,this relationship of movement vbeing sufficient to control the proper movement ofv the drive shaft and worms thereon.

If desired to provide for the release of the clutch 8d without the necessity of shifting the lever 14, a pedal P may be provided passing through an aperture in the floor and pivotally boards F of the vehicle,

L #nu mounted thereunder as at ic The pedal is connected by a lever 16D to a lever lwhich is inV turn connected or mountedupon ther shaft 9. VDepression of the pedal P will result lthrough the levers 161 and 16', in the The fulcrum 12@ of y y partial rotation of the shaft 9 to disengage the clutch 8d.

It will thus be clearlyl understood-that during the period of shifting from one speed to another, the shifting lever will be travelling in the slot 15a in the guide bracket 15, thus assuring that the shaft 9 will be rotated partially in proper' position to withdraw and retain. in withdrawn position-V through the clutch and clutch shiftingV me j fork-the driving gear 8 from the path of movement of the worms carried by the drive shaft. Upon the .release of the shaft 9 the driving gear will return to a position for engagement with the desired worm through the mechanism provided, and will approach the worm from the side and through the conformation of the teeth will Ireadily fall into mesh or engagement therewith.

It will be noted that all of the speeds of rotation of the driving gear through the variable speed transmission described in the present invention are directly driven from the power or engine shaft, thus 'providing an extremely quiet drive inl any speed or gear.

There has been `diagrammatically illustrated in Figures 14; and 15 of the drawings a method of developing a universal tooth for the driving gear capable of meshing or engaging with any desired one of the varying pitched worms. To this end each of the worms has the perpendicular distance between the teeth thereon identically constant. As shown in Figure 14 the lines R-R illustrate the angular development, properly pitched, of the space between teeth on the worm 5 controlling the reverse speed while the lines H-H illustrate the development also properly pitched of the space between teeth on the Worm 4 controlling the high speed; the line X-X being positioned to properly locate the peripheral vcenter line of the teeth on the driving gear 8. Each tooth f of the driving gear would accordingly be substantially diamond-shaped in cross section asr defined at T by the intersection of the lines R-R and H-I-T, the corners having been properly rounded. Tnasmuch as the angular development of the space between the teeth on any of the other worms would of necessity fall between the outermost of the lines H-H and R-R, such a tooth would securely mesh and have proper driving engagement with any desired one of the various worms.

There has thus been described a variable speed transmission of the worm type. wherein all speeds are directly driven from the 'power or engine shaft; wherein any shifting of gear or speed may be readily accomplished without danger of stripping of the worms or driving gear and without the difficulty or necessity of considering the relative speed of the vehicle with respect to the ,speed of rotationof the engine shaft; wherein the shifting or variation from a high to a lower gear may be as readily and conveniently made as from a low to a higher gear; wherein entirely automatic control of the clutch may be had, the clutch being located lat the driving gear; and wherein change of gearing is had by a continuous movement of the gear shift or control lever in a single direction.

-Tlie invention having thus been described, what is claimed is: i

l. In a variable speed transmission including driving mechanism comprising a power Shaft and a drive shaft carrying a plurality case, an integral sleeve extension on one side of the said differential gear case, a driving gear slidably mounted on said sleeve extension, a friction clutch connection'therebetween, means for bodily shifting the drive shaft longitudinally to selectively engageth-e Vworms thereon with the driving gear the said means being first operable to release the friction clutch and then to slidably withdraw the driving gear from the path of the worms on the drive lshaft during the shifting'op-v eration` y Y 2. In a variable speed transmission including driving mechanism comprising a power shaft and a drive shaft carrying a plurality of differently pitched worms mounted thereon, an extensible connection between said power and drive shafts,'a dri-ven member comprising a pair of axles provided at their adjacent extremities with a differential and differential'gear case, an integral sleeve extension on one side of the said differential gear case, a driving gear slidably mounted on said sleeve extension and adapted to engage with the worms on the drive shaft, a friction clutch connection between the driving gear and the sleeve extension on the differential gear case, means for bodily shifting the drive shaft longitudinally to selectively engage the wormsthereon with the driving gear the said means being first operable to release the friction clutch connection between the driving gearand the differential and then to slidably withdraw the driving gear from the path of the worms on the drive shaft during the shifting operation.

3. A variable speed transmissioncomprising a drive shaft carrying a plurality of worms, a driven shaft carrying a driving gear slidably mounted thereon adapted to mesh with the aforesaid forms, a friction clutch vconnection between said driving gear and driven shaft,` a countershaft having a .clutch fork mounted thereon adapted to control the aforesaid clutch, means for bodily shifting the drive shaft ylongitudinally'to selectively engage the worms on the drive shaft with the driving gear, said lmeans having an operative connectionk with the countershaft and being first operable to release the clutch and then slidably withdraw lit) the driving gear from the path ofthe worms on the. drive shaft duringthe shifting operation.

4. A variable speed transmission comprisiso ing a drive shaft carrying a plurality of worms, a driven shaft carrying a driving gear slidably mounted thereon adapted to engage with said worms, a` friction clutch connection between said di'iving gear and driven shaft, a countershaft having a clutch fork mounted thereon adapted to actuate the aforesaid clutch, means operatively connected with said coun-tershaft and operable to first release the aforesaid clutch and then Vbodily withdraw the driving gear from the pathof the worms on the drive shaft, the saidimeans having an operative connection with the driveshaft wherebythe said drive shaftmay be bodily shifted to selectively engage the worms thereon with the driving gear. V 5. A variable speed transmission including driving mechanism comprising a power shaft and a drive shaft carrying a plurality of differently pitched worms inountedrthereon, means for holding said drive shaft in desired positionincluding a. locking collar on ythe said drive shaft adapted to coact with stationary retaining members, an extensible connection between `such power and drive shafts, a driven shaft carrying a driving gearslidably mounted thereon and adapted to engage with theaforesaid worms, a friction clutch connection between said driving gear and driven shaft, a countershafthaving a clutch forl mounted thereon adapted to engage with said clutch, means operatively connected with said countershaft operable to first release the aforesaid clutch and then slidably withdraw the driving gear from the `path of the worms on the drive shaft, the

said means comprising a lever having an operative connection with the aforesaid locking collar on the drive shaft for bodily shifting the said drive shaft longitudinally to selectively engage the worms thereon with the driving gear.

6. A variableV speed transmission comprising a driving member including a power shaft and a drive shaft, an eXtensible connection therebetween, a, plurality of differently pitched worms carried by the drive shaft, means for holding the drive shaft in desired position comprising a locking collar mounted upon the said drive shaft and adapted to coact with stationary retaining members, a driven member comprising a pair 4of axles yprovided at their adjacent eX- treinities with a differential and a differential gear case, an integral sleeve extension at Amountedthereon adapted'to actuate the said f clutch, means operatively connected `with said countershaft operable tov vfirst release :the aforesaid clutch and then slidably withdraw the driving gear from the path of the worms on the drive shaft, lthe said means comprising a lever havingan'operative connection with the aforesaid locking collar on the drive shaft to bodily shift the drive shaft longitudinally to selectively engage the worms thereon with the driving gear.

7. A variable speed transmission comprising a driving member including a power shaft and adrive shaft having a plurality of differently pitched worms mounted thereon, means for holding the drive shaft in desired position comprising a locking member rigidly mounted upon the said drive shaft and adapted to coact with stationary retaining members an extensible connection between said power and drive shafts, a driven meinber comprising a pair of axles having their Ydjacent extremities provided witha differential and differential gear *case having an integral sleeve extension on Yone side thereof, a tubular member slidably mounted on said sleeve, a. driving gear freely mounted on said tubular member, a` friction clutch connection between said driving .gear and tubular member,aicountershaft having a clutch fori; mounted thereon adapted to actuate said clutch, means for bodily yshifting the drive shaft,longitudinallyr to selectively engage ther worms thereon with the `driving gear, said means `comprising a lever having an operative connection with the aforesaid local-r member carried by the drive shaft and said means being operatively connected with the countershaft and beinglirst operable to release the aforesaid clutch and then slidably withdraw the driving gear from thev path of the worms on the drive shaft during thesliifting operation.

8. A variable,` speed transmission coniprising a driving member including aA power shaft and a drive shaft having a plurality of differently pitched worms mounted thereon, means for holding` the drive shaft in desired position including a locking member rigidly secured upon the said drive. shaft and adapted to coact with stationaryretaining members, a tubular extensible driving connectionY between said power and drive shafts, a

Vdriven member comprisinfh a pair of'a-Xles provided at their adjacent 4extremities with a differential and differential gear case, having an integral sleeve extension at one side of the said gearcase, a second sleeve slidably mounted on said `first mentioned sleeve, a driving gear freely mounted on said second sleeve, a friction clutch connection between ysaid driving gear and said second sleeve,

a countershaft having a clutch fork mounted thereon adapted to `actuate the said clutch, means for bodily shifting the drive shaft longitudinally to selectivelyl engage the worms thereon with the driving gear, said means comprising a lever having an operaland then to slidably withdraw the driving gear from the path of the worms on th-e drive shaft during the shifting operation.

9. A variable speed transmission comprising a driving member including a power shaft and a drive shaft having a pluralityof differently pitched worms mounted thereon, means for holding the drive shaft in desired position, said means comprising a locking member carried by the drive shaft and adapted to co-act with stationary retaining members, a tubular extensible driving connection between said power and drive shafts, a driven member comprising a pair of axles Y provided at their adjacent extremities with a differential and differential gear case having an integral sleeve extension at one side y thereof, a second sleeve slidably mounted on said first mentioned sleeve, a driving gear freely mounted on said second sleeve, a friction clutch connection therebetween, a. countershaft having a clutch forkmounted thereon adapted to actuate said clutch, means comprising a. lever operatively connected with the countershaft and having an operative connection with the lock member car-v l0. In a variable speed vtransmission ofy the class described a drive shaft carrying a plurality of differently pitched worms ,mounted thereon and a driven shaft carry! ing a driving gear adapted to selectively mesh with said worms, the spaee'between teeth on each of the worms being identical and the distance between th-e center lines of ythe space between suoli teeth also being identical, the'teeth of the driving gear being disposed around tlie periphery thereof and being substantially diamond-shaped, the

angle between parallel sides of each tooth on the driving gear being determined by the greatest angular differ-ence between any two of the worms on the drive shaft.

1l. A variable speed transmission comprising a driving member including a power 'shaft and a. drive shaft having a plurality of differently pitched worms mounted thereon, means for holding the drive shaft in desired position, said means comprising a locking collar carried by the drive shaft and adapted to co-act with stationary retaining inembers, a tubular .extensible driving connection between the said power and drive shafts, a driven member comprising a pair of axles provided atktheir adjacent extremities with a differential and differential gear case, an integral sleeve extension on on-e side of the said differential gear case, a second sleeve slidably mounted on the first mentioned sleeve, a driving gear mounted for free rotation on said second sleeve, 'a clutch connection between said driving gear and secondsleeve the said clutch being slidably mounted on the said sleeve, a countershaft provided with a. clutch fork adapted to actuate the said clutch, means comprising al lever operatively connected with the countershaft and having an operative connection with the aforesaid locking collar for bodily shifting the drive shaft longitudinally toy selectively engage the worms thereon with the driving gear, the said means being rst operable to release the clutch and then slidably withdraw the aforementioned second sleeve and the driving gear thereon from the path of the worms on thedrive shaft during the shifting operation, the aforesaid locking f collar having an operative connection with the countershaft for releasing said locking collar during the shifting operation, and resilient means for returning the driving gear to engaging position. y

In testimony whereof he aiiixcs his signature.

ROSS H. PRATT. 

